Enhanced mineralization of [U-(14)C]2,4-dichlorophenoxyacetic acid in soil from the rhizosphere of Trifolium pratense

Shaw, L.J. and Burns, R.G. (2004) Enhanced mineralization of [U-(14)C]2,4-dichlorophenoxyacetic acid in soil from the rhizosphere of Trifolium pratense. Applied and Environmental Microbiology, 70 (8). pp. 4766-4774. ISSN 0099-2240. (The full text of this publication is not available from this repository)

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Abstract

Enhanced biodegradation in the rhizosphere has been reported for many organic xenobiotic compounds, although the mechanisms are not fully understood. The purpose of this study was to discover whether rhizosphere-enhanced biodegradation is due to selective enrichment of degraders through growth on compounds produced by rhizodeposition. We monitored the mineralization of [U-(14)C]2,4-dichlorophenoxyacetic acid (2,4-D) in rhizosphere soil with no history of herbicide application collected over a period of 0 to 116 days after sowing of Lolium perenne and Trifolium pratense. The relationships between the mineralization kinetics, the number of 2,4-D degraders, and the diversity of genes encoding 2,4-D/alpha-ketoglutarate dioxygenase (tfdA) were investigated. The rhizosphere effect on [(14)C]2,4-D mineralization (50 microg g(-1)) was shown to be plant species and plant age specific. In comparison with nonplanted soil, there were significant (P < 0.05) reductions in the lag phase and enhancements of the maximum mineralization rate for 25- and 60-day T. pratense soil but not for 116-day T. pratense rhizosphere soil or for L. perenne rhizosphere soil of any age. Numbers of 2,4-D degraders in planted and nonplanted soil were low (most probable number, <100 g(-1)) and were not related to plant species or age. Single-strand conformational polymorphism analysis showed that plant species had no impact on the diversity of alpha-Proteobacteria tfdA-like genes, although an impact of 2,4-D application was recorded. Our results indicate that enhanced mineralization in T. pratense rhizosphere soil is not due to enrichment of 2,4-D-degrading microorganisms by rhizodeposits. We suggest an alternative mechanism in which one or more components of the rhizodeposits induce the 2,4-D pathway.

Item Type: Article
Additional information: 0099-2240 (Print) Journal Article Research Support, Non-U.S. Gov't
Uncontrolled keywords: 2,4-Dichlorophenoxyacetic Acid/*metabolism Alphaproteobacteria/classification/*enzymology/genetics/isolation & purification Biodegradation, Environmental Carbon Radioisotopes/*metabolism Ketoglutarate Dehydrogenase Complex/genetics/metabolism Lolium/growth & development Molecular Sequence Data Plant Roots/*microbiology Polymerase Chain Reaction Polymorphism, Single-Stranded Conformational Sequence Analysis, DNA Soil/analysis *Soil Microbiology Species Specificity Trifolium/growth & development/*microbiology
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: Sue Davies
Date Deposited: 10 Sep 2008 14:42
Last Modified: 14 Apr 2014 10:34
Resource URI: http://kar.kent.ac.uk/id/eprint/6744 (The current URI for this page, for reference purposes)
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